Field of the Disclosure
Preferred embodiment of the present application relates to the art of a selectable one-way clutch adapted to selectively enable torque transmission only in one direction and to interrupt torque transmission in both directions.
Discussion of the Related Art
Japanese Patent Publication No. 5120650 describes a hybrid drive unit having a one-way clutch. According to the teachings of Japanese Patent Publication No. 5120650, in the one-way clutch an outer race connected to a motor-generator is allowed to rotate in the forward direction relatively to an inner race, but the inner race is inhibited to rotate in the counter direction relatively to the outer race.
A conventional selectable one-way clutch is adapted to selectively enable torque transmission only in one direction. To this end, in the selectable one-way clutch, a selector plate interposed between a pocket plate and a notch plate is rotated by an electromagnetic actuator or the like to selectively provide an engagement between the selector plate and the pocket plate. The selectable one-way clutch of this kind may also be used in the hybrid vehicle taught by Japanese Patent No. 5120650 instead of the one-way clutch.
In order to reduce friction, lubrication oil is applied to the selectable one-way clutch to form oil films in friction sites between the pocket plate and the selector plate, and between the selector plate and the notch plate. However, if viscosity of the oil is too high, the selector plate may be rotated undesirably by a drag torque or a shearing force resulting from rotation of the notch plate if the pocket plate is halted. For this reason, the pocket plate may be brought into engagement accidentally with the notch plate if temperature is extremely low.